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عنوان فارسی مقاله:
ارزیابی خارج شدن قطار باربری از خط برای ایمنی راه آهن و تحلیل ریسک
عنوان انگلیسی مقاله:
Freight-train derailment rates for railroad safety and risk analysis
سال انتشار : 2017
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مقدمه انگلیسی مقاله:
1. Introduction
Derailments are the most common type of train accident in the United States. They cause damage to infrastructure, rolling stock and lading, disrupt service, and have the potential to cause casualties and harm the environment. Understanding the most important factors affecting derailments is critical to development of effective risk reduction strategies. Train safety and risk analysis relies on accurate estimation of derailment rate, which is defined as the number of derailments normalized by some metric of traffic exposure, such as train-miles, car-miles or gross ton-miles (Nayak et al., 1983; Treichel and Barkan, 1993; Anderson and Barkan, 2004; Liu et al., 2011). Highway safety researchers have conducted a number of studies quantifying the relationship between accident rates and roadway design. These studies have considered the effects of road curvature,traffic volume, grade, shoulder width, number of lanes and other factors (e.g., Miaou, 1994; Maher and Summersgill, 1996; Hauer, 2001; Lord et al., 2005; Lord, 2006; Mitra and Washington, 2007). The earliest example of a comprehensive analogous study of railroad accident rates in the United States was conducted by Nayak et al. in the 1980s (Nayak et al., 1983). Using analyses of accident frequency and rail traffic volume, they found a strong statistical correlation between FRA track class and derailment rate. A subsequent unpublished study by Treichel and Barkan (1993) found a similar result and Anderson and Barkan (2004) used new data to develop updated estimates. All of these studies found that higher FRA track classes had lower derailment rates, varying by more than an order of magnitude. This relationship was not surprising; higher FRA track classes are intended to ensure safe operation at higher operating speeds and therefore require a variety of more stringent engineering safety and maintenance standards (FRA, 2011a). Nayak et al’s (1983) estimates, and the updates cited above, have been used by railroads, chemical companies, government agencies, researchers and others to address a variety of risk analysis and management questions (Glickman and Rosenfield, 1984; Rhyne, 1994; CCPS, 1995; ADL, 1996; STB, 2003; Kawprasert and Barkan, 2008, 2010). However, as the importance and sophistication of these questions has grown, so too has the importance of their accuracy. Simple predictive models of derailment rate based solely on a single parameter, FRA track class, might not satisfactorily account for all the pertinent factors. This led to closer scrutiny of other possible factors that might affect the relationship between FRA track class and derailment rate. Developing a better understanding of such relationships is important for improved railroad risk management practices. Since 1980 the U.S. railroad derailment rate has declined from 8.98 derailments per million train miles, to 1.63 in 2014, an 82% reduction (FRA, 1980, 2015). These derailment rates reflect statistics for all FRA track classes combined; however, they do not permit evaluation of the relative rate on different track classes, nor the possible effect of other factors. The relative importance of accident causes correlated with different track classes may co-vary with other factors and may shift as a result of changes in various factors (Anderson and Barkan, 2004). There is ongoing interest in improving rail safety and new concerns have been raised regarding the risk of rail transport of hazardous materials due to several fatal release accidents involving toxic inhalation hazard (TIH) materials in the mid-2000s, and more recent accidents resulting in large releases of flammable liquids. This prompted renewed interest in a more detailed understanding of the factors affecting derailment rate (Liu et al., 2012; Liu, 2015). In the same time frame, post-9/11 security concerns led the US Department of Transportation to promulgate new regulations that required railroads to conduct, “transportation route analysis, alternative route analysis, and route selection” for TIH materials (DOT, 2008). This led to new consideration of how to calculate derailment rate and whether it provided a sufficiently detailed means of assessing localized risk. Research by the authors of this paper suggested that other factors not previously considered might be affecting it as well, notably method of operation (i.e. traffic control system) and traffic density. Previous constraints on data systems and availability had limited the ability to consider more fine-grained questions regarding factors that might co-vary with track class and affect derailment rate. Furthermore, these analyses had used relatively simple statistical techniques that were not capable of detecting the complex relationship between derailment rates and multiple influencing factors. To address these questions, a new dataset was developed that contained information on FRA track class, method of operation and traffic density.
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